Electromechanical and magnetic properties of BiFeO3-LaFeO3-CaTiO3 ceramics near the rhombohedral-orthorhombic phase boundary

BiFeO3-LaFeO3-CaTiO3 ceramics have been studied by X-ray diffraction, magnetization measurements, and piezoresponse force microscopy (PFM). The compositional ranges of the polar, antipolar, and non-polar phases have been estimated. PFM measurements testify gradual decrease of piezoelectric response in Bi(0.85-x)La(0.15)CaxFe(1-x)Ti(x)O(3) system with Ca/Ti content increase, except a narrow concentration region near polar-antipolar phase boundary where piezoelectric signal shows maximum value. It is found that increase of dopant concentration leads to apparent decrease of the off-center Bi-O displacement and, consequently, causes a reduction of piezoelectric response. It is concluded that notable remanent magnetization in polar and non-polar structural phases is a result of the Dzyaloshinsky-Moria interaction. (C) 2013 AIP Publishing LL

Ferroelectric nanocomposites based on polymer ferroelectrics and graphene/oxide graphene: Computer modeling and SPFM experiments

The authors are thankful to the Russian Science Foundation (RSF grant # 16-19-10112) and to the Russian Foundation for Basic Researches (RFBR grants # 16-51-53917) for support. Prof. Xiang-Jian Meng expresses his gratitude to the National Natural Science Foundation of China (NNSFC) for support of the project: "The study on the new type of infrared detector based on ferroelectric tunnel junction"

Intermediate structural state in Bi1−xPrxFeO3 ceramics at the rhombohedral–orthorhombic phase boundary

Crystal structure of the Bi1−xPrxFeO3 ceramics of the compositions corresponding to the threshold concentrations separating the polar rhombohedral (R3c) and anti-polar orthorhombic (Pbam) phases has been investigated with X-ray diffraction, transmission electron microscopy and differential scanning calorimetry measurements performed in a broad temperature range. The structural study specifies the peculiarities of the temperature-driven transition into the non-polar orthorhombic (Pnma) phase depending on the structural state of the compounds at room temperature. The crystal structure analysis reveals the revival of the anti-polar orthorhombic phase upon the temperature-induced transition, thus assuming that it can be considered as the bridge phase between the polar rhombohedral and the non-polar orthorhombic phases.publishe

Local study of the domain wall mobility in ferroelectric ceramics under the action of electric field and mechanical loading

The equipment of the Ural Center for Shared Use “Modern nanotechnology” was used. The reported study was funded by RFBR (grant No. 17-52-04074) and BRFFR (grant No. F17RM-036). This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 778070

Peculiarities of the crystal structure evolution of Bifeo3-batio3 ceramics across structural phase transitions

Evolution of the crystal structure of ceramics BiFeO3-BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral-cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN: UID/04564/2020, UIDB/50011/2020, UIDP/50011/2020Russian Science Foundation, RSF: 18-19-00307Funding: This work was supported by the RSF (project #18-19-00307). Investigations performed at the Center for Physics of the University of Coimbra were supported by Fundação para a Ciência e a Tecnologia (project UID/04564/2020). M.V.S. acknowledges Russian academic excellence project “5-100” for Sechenov University. Part of work done at the University of Aveiro was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC

Mn substitution-modified polar phase in the Bi1-xNdxFeO3 multiferroics

Room-temperature crystal structure and multiferroic properties of the Bi0.92Nd0.08Fe1-xMnxO3 (x <= 0.3) ferromanganites have been studied to reveal the effect of Mn doping on the magnetic and ferroelectric behaviors of the lanthanide-modified compound representing a polar (space group R3c) predominantly antiferromagnetic phase of the Bi(1-x)Ln(x)FeO(3) perovskites. B-site substitution tends to suppress existing polar displacements and induces a ferroelectric-to-antiferroelectric transition near x = 0.2. The threshold concentration inducing the structural transformation does not coincide with that required to change the dominant magnetic interaction, so a weak ferromagnetic/ferroelectric state unusual for the Bi(1-x)Ln(x)FeO(3) and BiFe1-xMnxO3 series appears in the intermediate concentration range near the polar/nonpolar phase boundary. (C) 2013 AIP Publishing LLC

Piezoelectric resonators based on self-assembled diphenylalanine microtubes

Piezoelectric actuation has been widely used in microelectromechanical devices including resonance-based biosensors, mass detectors, resonators, etc. These were mainly produced by micromachining of Si and deposited inorganic piezoelectrics based on metal oxides or perovskite-type materials which have to be further functionalized in order to be used in biological applications. In this work, we demonstrate piezoelectrically driven micromechanical resonators based on individual self-assembled diphenylalanine microtubes with strong intrinsic piezoelectric effect. Tubes of different diameters and lengths were grown from the solution and assembled on a rigid support. The conducting tip of the commercial atomic force microscope was then used to both excite vibrations and study resonance behavior. Efficient piezoelectric actuation at the fundamental resonance frequency approximate to 2.7 MHz was achieved with a quality factor of 114 for a microtube of 277 mu m long. A possibility of using piezoelectric dipeptides for biosensor applications is discussed. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793417